The present invention is directed to a liquid filtration system and to a method of treating the liquid in the enclosed system.
Filter assemblies are commonly used to protect combustion engines by filtering out contaminants and thereby preventing damage to the engine and other downstream components such as valves, fuel injectors, fuel lines, and related other components. To maintain engine performance and reliability, the filter assemblies must be replaced, often as frequently as every 2,000 to 4,000 vehicle miles.
It can be equally important to add agents to the fuel to reduce damage to the engine and related downstream components and/or to enhance the performance of the engine. For example, since the early 1990's diesel fuel producers have significantly reduced the sulfur content in diesel fuel to reduce the environmental harm that was attributed to the burning of high sulfur content fuels. However, the naturally occurring sulfur in the diesel fuel also acted as a lubricant. The resulting low sulfur content diesel fuel caused increased wear on the diesel engine and, in particular, to the fuel pump and injectors, which in turn caused significant harm to the overall operation, performance, and efficiency of the engine and even to the environment. Consequently, various additives were developed to increase not only the lubricity but also to enhance fuel stability, fuel combustion, and engine performance.
It is difficult to maintain a constant or desired level of the additive in the fuel. Typically an operator adds a bottled additive or additive concentrate to the vehicle fuel tank with each fuel fill-up. While many bottled fuel additives are commercially available, often operators do not consistently add the additive with each fill-up—the additive might not be readily available or the operator may forget to include the additive. Combining the additive with fuel in the fuel tank may not reliably provide a homogenous fuel/additive mixture.
Fuel tanks do not include reliable methods for mixing fuel. Generally operators rely upon the turbulence created during a fill-up and by vehicle motion to mix the additive and fuel. Furthermore, the additive concentration in the fuel may vary, depending upon the amount of fuel in the fuel tank—assuming a set amount of additive is added with each fill-up.
Various alternative methods have been developed to add the additives to fuel. One method includes providing a fuel additive in a filter assembly such as disclosed in U.S. Pat. No. 6,238,554 issued to Martin et al., which adds the additive to the fuel under diffusion-controlled conditions.
Another method is disclosed by Davis in U.S. Pat. No. 5,507,942, which includes a filter assembly with a solid fuel additive that dissolves in the fuel as the additive contacts the fuel in the filter assembly.
The present invention provides a novel method of treating fuel by capitalizing on the existence of or developing a fluid pressure gradient within the filter assembly. The pressure gradient can then be harnessed to continuously add the fuel additive to the fuel flowing through the filter assembly. Consequently, the present invention provides novel advancements and additionally provides a wide variety of benefits and advantages in the relevant subject matter.
While the above discussion has been directed toward filter assemblies, the present invention provides a novel filter assembly and method of treating the fluid flowing through that filter, regardless of whether that liquid is a fuel. The principles embodied in the present invention apply to filters in general and can be used in filter assemblies, air filters, lubricant filters, and/or coolant filters.